Identity protocol v1

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Revision as of 04:22, 28 June 2013 by Jgarzik (talk | contribs) (Creating sacrifice transactions: prefer block height)
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Design goals

Decentralized identity.

  • Has some creation cost
  • Sacrifice may be digitally proven, bootstrapping root of trust from blockchain data
  • Start as anonymous; opt out of anonymity by attaching identifying key-value pairs ( = "John Smith").

Creating sacrifice transactions

Similar to Announce/Commit Sacrifices

  1. TM = current block height
  2. create transaction T2.
    1. must include OP_RETURN <digest of master pubkey>
    2. nlocktime = TM + 144 blocks
    3. no more than 1000 bytes in size
  3. create transaction T1
    1. must include >= 0.01 BTC fee
    2. must include OP_RETURN txid(T2)
    3. no more than 1000 bytes in size
  4. broadcast T1, T2 until confirmed

Creating root record

Craft a bytestream that represents the root SIN record.

  1. B1 = block w/ T1, B2 = block w/ T2
  2. Verify B2 time >= (24-4) hours B1 time. Fail and waste sacrifice if not.
  3. MD = ripemd160(B1.hash + T1.txid + B2.hash + T2.txid)
  4. Prefix = 0x18, SIN_Version = 0x01
  5. SIN = base58_encode_check( Prefix + SIN_Version + MD )
  6. PPK = Preferred Public Key, new public key for root of trust
  7. Build root record,
    1. root = SIN + PPK
    2. H_ROOT = hash(root)
    3. For each (T1, T2), -- prove we control 100% of the inputs for T1, T2
      1. For each input
        1. Obtain referenced output
        2. Obtain public key from output (if necessary, look up in local node db from pubkeyhash)
        3. signature = sign H_ROOT with key associated with just-retrieved public key
        4. root += (public key, signature)

Thus a minimal root record is

  • SIN
  • PPK
  • list of (public key, signature)

and is provably

  • linked to the sacrifices
  • PPK starts a new chain of digital signature trust, for further record updates

After that, additional key-value pairs may be associated with the root record via updates verified by PPK, stored in an alt-blockchain or DHT somewhere. That is outside the scope of this minimal document.